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1

The use of a rotary impact testing machine in tests of materials under dynamic strain conditions

Hyc-Dadak Katarzyna, Pawlicki Jacek

Biuletyn Instytutu Spawalnictwa w Gliwicach

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2023

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Vol. 67, No. 3

44--50

EN

The article presents characteristics of an upgraded rotary impact testing machine featuring a new measurement system based on strain gauges and enabling the recording of short signals. A dedicated test rig enabled the performance of dynamic tensile and bend tests within a linear velocity of a forcing element (striker/claw) restricted within the range of 5 m/s to 40 m/s. Tests involved TRIP and DP steels as well as alloys of non-ferrous metals PA4 and AZ31. Dynamic tensile tests were performed in relation to a striker linear velocity of 5 m/s, 15 m/s and 30 m/s. The results obtained in the above-named tests were compared with those obtained in static tensile tests. The dynamic tensile tests and structural examinations made it possible to identify correlations between strain rates, mechanical properties of the materials and the morphology of fractures. The testing methodology discussed in the article could constitute an effective tool enabling the assessment of properties of structural materials under dynamic strain conditions. The research-related test results could be used when designing the structure of energy-consuming elements of vehicles and load-bearing elements of aircraft exposed to dynamic loads.

PL

W artykule przedstawiono charakterystykę zmodernizowanego młota rotacyjnego wyposażonego nowy system pomiarowy, oparty na czujnikach tensometrycznych, umożliwiający rejestrację krótkotrwałych sygnałów. Stanowisko umożliwia przeprowadzenie prób dynamicznego rozciągania i zginania w zakresie prędkości liniowej elementu wymuszającego od 5 do 40 m/s. Badania przeprowadzono dla wybranej grupy materiałów metalicznych stali TRIP i DP oraz stopów metali nieżelaznych PA4 i AZ31. Próby dynamicznego rozciągania wykonano dla prędkości liniowej bijaka: 5, 15 i 30 m/s. Otrzymane wyniki porównano z uzyskanymi w warunkach statycznej próby rozciągania. Przeprowadzone próby dynamicznego rozciągania oraz badania strukturalne pozwoliły na określenie zależności pomiędzy prędkością odkształcenia a własnościami wytrzymałościowymi materiałów oraz morfologią przełomów. Zaproponowana metodyka badań materiałów może stanowić efektywne narzędzie do oceny właściwości materiałów konstrukcyjnych w warunkach dynamicznego przebiegu odkształcenia. W praktyce wyniki badań mogą być stosowane do projektowania konstrukcji elementów energochłonnych pojazdów i elementów nośnych statków powietrznych, poddanych dynamicznym obciążeniom.

2

Experimental study on the dynamic tensile mechanical properties of marble under water and oil conditions

Li Chaoxin, Liu Dongyan, Zhu Yunhui

Archives of Civil Engineering

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2023

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Vol. 69, nr 3

317--330

EN

To investigate the dynamic tensile properties and energy dissipation characteristics of marble in three different conditions: dry, water-saturated, and oil-saturated, a Brazilian disk splitting test was conducted using a 50 mm diameter Hopkinson pressure bar (SHPB) device. The findings indicate that the peak strain and dynamic tensile strength of the three conditions increase with strain rate, exhibiting a clear strain rate effect. Additionally, lubricating effects of water and oil weaken internal shear sliding friction, thus promoting crack expansion. Furthermore, immersion of fluid in marble weakens the cementation of internal mineral particles, leading to lower tensile strength of marble saturated with water and oil compared to dry marble under dynamic impact. When analyzing the energy dissipation of marble, both the absorption energy and dissipation energy density increase with oil strain rate, indicating a positive correlation. Moreover, numerical results obtained from ANSYS/LS-DYNA correspond well with experimental data, thus verifying and interpreting the experimental outcomes.

3

AA5052 failure prediction of electromagnetic flanging process using a combined fracture model

Deng Huakun, Mao Yunfei, Li Guangyao, Zhang Xu, Cui Junjia

Archives of Civil and Mechanical Engineering

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2022

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Vol. 22, no. 2

art. no. e84, 1--17

EN

Electromagnetic forming process could significantly increase the forming limit of aluminum alloy. However, high-speed fracture prediction of aluminum alloys is a major problem in the development of electromagnetic flanging process. In this study, notched specimen tensile tests with high-speed Digital Image Correlation system were conducted under the strain rate range from 0.001 to 100 s-1. A fracture model of AA5052 alloys which combined of an uncoupled fracture model, Gissmo damage evolution model and Johnson-Cook strain rate effect was established. Electromagnetic flanging experiments were conducted to verify the failure criteria effectiveness. Results showed that failure strain was significantly influenced by strain rate under various loading path. Compared with the experiments, the percentage error of established electromagnetic flanging process FEM model was less than 4%. The fracture model established could well predict notched specimen high-speed failure, and also accurately predict sheet failure model of electromagnetic flanging experiments and, thus, verified the effectiveness of the established dynamic failure criteria in electromagnetic flanging process.